1. Field of the Invention
This invention relates to a dental handpiece for retaining a conventional dental bur or similar workpiece and to an improved release means by which the bur can be easily removed from the handpiece while minimizing the manual pushing force that is necessary to actuate the release means.
2. Background Art
Compressed air driven dental handpieces have long been used by dental workers to treat the teeth of their patients. One of a variety of workpieces (e.g. a dental bur) is releasably connected to a hollow cylindrical collet of the handpiece so as to be rotatable in response to a corresponding rotational force that is applied to the collet.
From time-to-time, it is necessary to remove the dental bur from the handpiece for purposes of repair, cleaning or replacement by a different workpiece. To accomplish the foregoing, the dental worker typically exerts a pushing force against a push-button of the handpiece which is ultimately transmitted to the collet so as to cause the collet to release its grip on the bur. However, it has been found that a large pushing force is often required before the bur will be released by the collet. Such a large pushing force has heretofor been necessary because of the shape of a collet actuator of the handpiece that transmits the pushing force from the push-button to the collet. More particularly, one well known collet actuator has a pair of wedge-shaped tips that form relatively large angles of about 30 degrees. The collet actuator is moved axially by the push-button so that the wedge shaped tips thereof are received by the hollow cylindrical collet to cause flexible clamping fingers of a collet to rotate outwardly and thereby release their grip upon the bur.
As a consequence of the large angle of the wedge-shaped tips of the collet actuator and the large pushing force that is transmitted to the collet, the flexible clamping fingers of the collet have been known to rotate through a correspondingly large arc. On occasion, this large rotation has significantly reduced the spring-like memory of the flexible clamping fingers of the collet. In this case, the collet may become deformed which undesirably effects its ability to reliably retain a dental workpiece between the flexible clamping fingers. Accordingly, it may be necessary to repair the dental handpiece and/or replace the collet which increases both the cost and downtime to the dental worker.
What is needed is a dental handpiece having an improved workpiece (e.g. bur) release means that reduces the manual pushing force required to release the workpiece as well as the likelihood that the collet will be deformed as the workpiece is released.